I know theres something that is smallest because it would eventually be nothing if there wasnt a limit. Unless negative mass is what I think it is, then there would be no limit to how small something could get. Is negative mass what Im thinking it is? Please explain negative mass.

Preons are hypothetical particles which would be constituents of quarks and leptons. However there is no experimental evidence to support the theory. You can get a detailed history of the this theory from wikipedia.